Fix for occasional divide-by-zero in filer copies

An else clause was being run for both the "write not complete" case but also when an error had occurred in an earlier step. The error would generally be a failure to create and hence a file size of zero. Bang.
Steps to recreate (other, more obscure and hard to catch cases exist)
 1. Open ResourceFS
 2. Copy Resources:$.Resources to Resources:$.Apps
 3. As ResourceFS is read only the reads all buffer OK but the first write (should return 'read only') gives divide-by-zero

Version 0.59. Tagged as 'FilerAct-0_59'

Syntax

-Syntax: *Filer_Action

VersionASM

@@ -11,13 +11,13 @@
                         GBLS    Module_HelpVersion
                         GBLS    Module_ComponentName
                         GBLS    Module_ComponentPath
-Module_MajorVersion     SETS    "0.58"
-Module_Version          SETA    58
+Module_MajorVersion     SETS    "0.59"
+Module_Version          SETA    59
 Module_MinorVersion     SETS    ""
-Module_Date             SETS    "16 Aug 2012"
-Module_ApplicationDate  SETS    "16-Aug-12"
+Module_Date             SETS    "05 Apr 2013"
+Module_ApplicationDate  SETS    "05-Apr-13"
 Module_ComponentName    SETS    "FilerAct"
 Module_ComponentPath    SETS    "castle/RiscOS/Sources/Desktop/FilerAct"
-Module_FullVersion      SETS    "0.58"
-Module_HelpVersion      SETS    "0.58 (16 Aug 2012)"
+Module_FullVersion      SETS    "0.59"
+Module_HelpVersion      SETS    "0.59 (05 Apr 2013)"
                         END

VersionNum

-/* (0.58)
+/* (0.59)
  *
  * This file is automatically maintained by srccommit, do not edit manually.
  * Last processed by srccommit version: 1.1.
  *
  */
-#define Module_MajorVersion_CMHG        0.58
+#define Module_MajorVersion_CMHG        0.59
 #define Module_MinorVersion_CMHG        
-#define Module_Date_CMHG                16 Aug 2012
+#define Module_Date_CMHG                05 Apr 2013
 
-#define Module_MajorVersion             "0.58"
-#define Module_Version                  58
+#define Module_MajorVersion             "0.59"
+#define Module_Version                  59
 #define Module_MinorVersion             ""
-#define Module_Date                     "16 Aug 2012"
+#define Module_Date                     "05 Apr 2013"
 
-#define Module_ApplicationDate          "16-Aug-12"
+#define Module_ApplicationDate          "05-Apr-13"
 
 #define Module_ComponentName            "FilerAct"
 #define Module_ComponentPath            "castle/RiscOS/Sources/Desktop/FilerAct"
 
-#define Module_FullVersion              "0.58"
-#define Module_HelpVersion              "0.58 (16 Aug 2012)"
-#define Module_LibraryVersionInfo       "0:58"
+#define Module_FullVersion              "0.59"
+#define Module_HelpVersion              "0.59 (05 Apr 2013)"
+#define Module_LibraryVersionInfo       "0:59"

c/memmanage

@@ -1247,9 +1247,8 @@ os_error *read_a_block( BOOL *i_am_full, BOOL *need_another_file, BOOL *that_fin
         */
         if ( next_fh_to_read() == NULL )
             *need_another_file = Yes;
-
-    #ifdef USE_PROGRESS_BAR
     }
+    #ifdef USE_PROGRESS_BAR
     else
     {
         uint64_t p;
@@ -1262,8 +1261,8 @@ os_error *read_a_block( BOOL *i_am_full, BOOL *need_another_file, BOOL *that_fin
         *progress = (uint32_t) p;
 
         debugmem(( "partial read: %u bytes / %u = %08x progress\n", b, fh->size, *progress ));
-    #endif
     }
+    #endif
 
     debugmem(( "X\n" ));
 
@@ -1595,23 +1594,24 @@ static os_error *int_write_a_block( BOOL *i_am_empty, BOOL *that_finished_a_file
         #endif
 
         remove_file_from_chain();
-
-    #ifdef USE_PROGRESS_BAR
     }
+    #ifdef USE_PROGRESS_BAR
     else
     {
-      uint64_t p;
-      uint32_t b;
+        uint64_t p;
+        uint32_t b;
 
-      b = fh->written_to - start_written_to;
-      p = (fh->total_progress * (uint64_t)b) / fh->size;
+        if ( err ) return err;
 
-      fh->write_progress -= (uint32_t) p;
-      *progress = (uint32_t) p;
+        b = fh->written_to - start_written_to; /* bytes written this time */
+        p = (fh->total_progress * (uint64_t)b) / fh->size;
 
-      debugmem(( "partial write: %u bytes / %u = %08x progress\n", b, fh->size, *progress ));
-    #endif
+        fh->write_progress -= (uint32_t) p;
+        *progress = (uint32_t) p;
+
+        debugmem(( "partial write: %u bytes / %u = %08x progress\n", b, fh->size, *progress ));
     }
+    #endif
 
     debugmem(( "X\n" ));